Gents
Mike makes some good points, but I think Rob's point was not to teach known abusers from the arts. A rather simple point.
There are those I would NEVER teach that made it to internal arts seminars. Vetting students is as problematic as vetting teachers. It's why I spent 18yrs with a closed door policy. If you weren't vetted you didn't get in. I've made few exceptions, even with this new openness thing I'm doing. You've much better chances knowing someone who knows me to get in the door.
As for vetting, I'm having a somewhat similar conversation on E-budo. I don't like overly stressing a one-sided view. Over there it seems every time you mention Koryu, its like flicking on a switch, "....students are ill resolved, spiritually inept, they can't submit to a teacher, they have no discipline, they don't underst.../ switch off.

I'd hate to see the same thing here seemingly sounding like you have to be this way or that way to be competent or even incompetent. There are incompetent A-hole teachers, defending their turf, and position who also simply suck and not worth knowing. There are highly competent teachers who are nice people. There are also extremely good fighters who also teach who are nice, and some very dangerous and abusive fighters as well.
There is no jack-ass test to be a teacher or student.
Pigeonholing personality types doesn’t work.

I've met any manner of highly competent teachers who were wonderful, magnanimous people; including two Japanese Koryu teachers who could light up a room with their personality, this was echoed in Lou Cheng De who was simply one of the warmest souls you could meet. Both of whom could deliver power and skill. And another Koryu teacher who is open, giving and hilariously funny as well as exceptionally good at teaching. Yes there are teachers, who are cantankerous A-holes, but I don't give a rat’s ass and I've told them so to their face.

Do we have to apologize for having a warm personality? And can't it go hand in hand with sound judgment, and discernment in who you teach? I think so. FWIW, showing something once to someone, is not teaching them-that happens over time. I’ve shown people things, while being super nice, to let them know their place...in a pecking order they may not have been aware even existed, and that maybe they had better think twice about opening their mouths. And then never said a word to anyone about it.

So, while I accept that there are defensive, protectionist, abusing jackasses in the arts-I've met more than a few, and would never show them anything- perhaps the over-riding point here should be to realize …
You don’t have to be one of them!
Rant-off